What - season 3~4 Ex Calling?
That thing was terrible. In any situation it wasn't a complete waste of gold, there was always a better item.
1.5 second duration.
Only applies with auto-attacks.
That made the healing debuff essentially useless vs. in-lane sustain, useless vs. passive on champions like Mundo, Cho'Gath, Garen, Irelia, Aatrox, useless vs. healing potions, useless vs. in-lane healing via someone like Nami, Sona, Soraka, Alistar, Taric.
With 1.5 seconds - it wasn't even good at stopping last-ditch healing escapes. You stop like, "1" tick of Volibear's passive.
Not to mention a 1.5 second duration forced you to focus-fire a sustain-monster like Mundo for the passive to be useful - and focusing someone like Mundo isn't a tactically sound decision in several instances, which really limited the items already limited uses.
The only type of sustain Ex Calling was good against was life-steal in a direct PvP battle or a Heal bait, and that's pretty much it.
And when it comes to stopping life steal - nothing's better than Thornmail. Due to how it works, it's pretty much impossible to life-steal off of someone wearing thornmail. And armor already mitigates life steal - reducing a 100 damage attack to a 50 damage attack means that 20% life steal drops from restoring 20 HP a hit to only 10.
Anyways - Ex Calling was pretty terrible, at least in it's season 3~4 iteration. I'm honestly surprised Riot kept it in the game for season 4, as if I'm not mistaken it was already the least purchased item in the game at the end of season 3 (probably due to some of the above reasons).
All I can really see adding Ex Calling back into the game accomplishing is adding a greater burden of knowledge for new players to have to deal with, and an extra item to have to sort through when looking for something useful for veteran players.